reyOS is for me to experiment with OS building. As of now I have little to no experience so don't take this to seriously :). I am running Debian, so all is only tested and build on Debian.
source the environment file to setup all the environment variables, then run ./setup-toolchain. This wil prepare the complete toolchain that you need in the toolchain folder (this takes a while, as it compiles a compiler). Note: this will also install some apt dependencies. Now run tup init and everything can be compiled by simply running tup!
To run reyOS you need qemu (or a i686 pc if you are feeling adventurous). When installed run:
qemu-system-i386 -cdrom reyOS.iso